You haven't mentioned the time that you will spend in Europe, which makes any comments about your route plan difficult as I cannot say if it is too packed or not, but in general I think it is a pretty good route. Just take it easy and make sure you leave yourself enough time to enjoy in every country/place to actually get the real experience of it - leave time to speak to locals and just wonder around in the cities, not just only touristy stuff. One thing though would be that I would skip Milan as it is nothing special compared to the other places that you are planning on going. It is just another gorgeous looking Italian cities, but it doesn't have much history or places to visit, it is more for shopping (and many of them are very expensive brand shops) or then for opera (because we cannot forget La Scala! :D). You could get instead of Milan more time in the other places. Also I would recommend to check out the countryside and take day trips out of the cities you are planning to visit, like in Florence definitely go visit Tuscany and the other regions surrounding it (Pisa, San Marino, Lucca etc) as the views are gorgeous and you also experience the real Italian life in the villages or smaller towns. Same with Nice, I would suggest you to check out the whole region of Provence, go to St.Tropez, Marseille, Cannes and the smaller places. Again you will experience the whole French life. And most importantly - have fun and don't try to fit too much into, it is ok not to get to do everything!